Abstract: California exports at least $3 billion USD annually of tree nuts, predominately
almonds, walnuts, and pistachios. Navel orangeworm (NOW), Amyelois transitella (Walker)
(Lepidoptera: Pyralidae), is the primary insect pest, infesting nuts in the orchard as well as those routed into packing operations and subsequently marketing channels. Certain importing countries demand a phytosanitary treatment be conducted to control NOW. Postharvest fumigation with methyl bromide, propylene oxide, sulfuryl fluoride, and phosphine are used to disinfest tree nuts upon arrival at the pack house, however, consumer and regulatory demand for an “organic” disinfestation is considerable. This research evaluates NOW control following exposure to low-oxygen mixtures (i. e., < 1 % v/v, 10,000 ppmv) having various balances of nitrogen and carbon dioxide, using a steady-state application system. Results from this laboratory-scale research predicate the parameters required for confirmatory testing and commercial/operational performance with respect to phytosanitary adoption of controlled atmosphere treatments, particularly for quarantine scenarios.